In using opto-electronic transducers such as charge-coupled devices ("CCDs") to obtain three-dimensional video-type data of a patient's tooth structure and in using that data to control tooth preparation and even the preparation of dental prostheses for attachment to the tooth, it is helpful and generally necessary for a computer to be provided with exact dimensions of the tooth. In brief, the video data pertaining to the tooth surface structure is best provided with a distance reference at the tooth surface. Such a distance reference enables the computer operating on the three-dimensional surface data to calculate exact dimensions of various tooth features.
Three-dimensional surface data may also be gathered by tracing the surface(s) of the tooth along a multiplicity of contours. The contour data is then automatically fed to a computer for use in generating an eletronically implemented three-dimensional representation of the tooth surface.
It has been found that such contour data is utilizable by conventional CAD/CAM programming only with significant difficulty unless the contour data comprises sets of parallel contours along the tooth surface.